-Wwrite-strings: Add a PyArg_ParseTupleAndKeywords "const char *" overload

-Wwrite-strings flags code like:

   static char *keywords[] = {"command", "from_tty", "to_string", NULL };

as needing "(char *)" casts, because string literals are "const char []".

We can get rid of the casts by changing the array type like this:

 -  static char *keywords[] = {"command", "from_tty", "to_string", NULL };
 +  static const char *keywords[] = {"command", "from_tty", "to_string", NULL };

However, passing the such array to PyArg_ParseTupleAndKeywords no longer
works OOTB, because PyArg_ParseTupleAndKeywords expects a "char **":

  PyArg_ParseTupleAndKeywords(PyObject *args, PyObject *kw,
                              const char *format,
			      char *keywords[], ...);

and "const char **" is not implicitly convertible to "char **".  C++
is more tolerant that C here WRT aliasing, and a const_cast<char **>
is fine.  However, to avoid having all callers do the cast themselves,
this commit defines a gdb_PyArg_ParseTupleAndKeywords function here
with a corresponding 'keywords' parameter type that does the cast in a
single place.

gdb/ChangeLog:
2017-04-05  Pedro Alves  <palves@redhat.com>

	* python/python-internal.h (gdb_PyArg_ParseTupleAndKeywords): New
	static inline function.
	* python/py-arch.c (archpy_disassemble): Constify 'keywords'
	array and use gdb_PyArg_ParseTupleAndKeywords.
	* python/py-cmd.c (cmdpy_init): Likewise.
	* python/py-finishbreakpoint.c (bpfinishpy_init): Likewise.
	* python/py-inferior.c (infpy_read_memory, infpy_write_memory)
	(infpy_search_memory): Likewise.
	* python/py-objfile.c (objfpy_add_separate_debug_file)
	(gdbpy_lookup_objfile): Likewise.
	* python/py-symbol.c (gdbpy_lookup_symbol)
	(gdbpy_lookup_global_symbol): Likewise.
	* python/py-type.c (gdbpy_lookup_type): Likewise.
	* python/py-value.c (valpy_lazy_string, valpy_string): Likewise.
	* python/python.c (execute_gdb_command, gdbpy_write, gdbpy_flush):
	Likewise.

1 files changed, 16 insertions, 17 deletions

diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
index 77fc543..4b43c54 100644
--- a/gdb/python/py-inferior.c
+++ b/gdb/python/py-inferior.c
@@ -435,10 +435,10 @@ infpy_read_memory (PyObject *self, PyObject *args, PyObject *kw)
   CORE_ADDR addr, length;
   gdb_byte *buffer = NULL;
   PyObject *addr_obj, *length_obj, *result;
-  static char *keywords[] = { "address", "length", NULL };
+  static const char *keywords[] = { "address", "length", NULL };
 
-  if (! PyArg_ParseTupleAndKeywords (args, kw, "OO", keywords,
-				     &addr_obj, &length_obj))
+  if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "OO", keywords,
+					&addr_obj, &length_obj))
     return NULL;
 
   if (get_addr_from_python (addr_obj, &addr) < 0
@@ -494,21 +494,20 @@ infpy_write_memory (PyObject *self, PyObject *args, PyObject *kw)
   const gdb_byte *buffer;
   CORE_ADDR addr, length;
   PyObject *addr_obj, *length_obj = NULL;
-  static char *keywords[] = { "address", "buffer", "length", NULL };
+  static const char *keywords[] = { "address", "buffer", "length", NULL };
 #ifdef IS_PY3K
   Py_buffer pybuf;
 
-  if (! PyArg_ParseTupleAndKeywords (args, kw, "Os*|O", keywords,
-				     &addr_obj, &pybuf,
-				     &length_obj))
+  if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "Os*|O", keywords,
+					&addr_obj, &pybuf, &length_obj))
     return NULL;
 
   buffer = (const gdb_byte *) pybuf.buf;
   buf_len = pybuf.len;
 #else
-  if (! PyArg_ParseTupleAndKeywords (args, kw, "Os#|O", keywords,
-				     &addr_obj, &buffer, &buf_len,
-				     &length_obj))
+  if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "Os#|O", keywords,
+					&addr_obj, &buffer, &buf_len,
+					&length_obj))
     return NULL;
 
   buffer = (const gdb_byte *) buffer;
@@ -643,7 +642,7 @@ infpy_search_memory (PyObject *self, PyObject *args, PyObject *kw)
 {
   struct gdb_exception except = exception_none;
   CORE_ADDR start_addr, length;
-  static char *keywords[] = { "address", "length", "pattern", NULL };
+  static const char *keywords[] = { "address", "length", "pattern", NULL };
   PyObject *start_addr_obj, *length_obj;
   Py_ssize_t pattern_size;
   const gdb_byte *buffer;
@@ -652,9 +651,9 @@ infpy_search_memory (PyObject *self, PyObject *args, PyObject *kw)
 #ifdef IS_PY3K
   Py_buffer pybuf;
 
-  if (! PyArg_ParseTupleAndKeywords (args, kw, "OOs*", keywords,
-				     &start_addr_obj, &length_obj,
-				     &pybuf))
+  if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "OOs*", keywords,
+					&start_addr_obj, &length_obj,
+					&pybuf))
     return NULL;
 
   buffer = (const gdb_byte *) pybuf.buf;
@@ -663,9 +662,9 @@ infpy_search_memory (PyObject *self, PyObject *args, PyObject *kw)
   PyObject *pattern;
   const void *vbuffer;
 
-  if (! PyArg_ParseTupleAndKeywords (args, kw, "OOO", keywords,
- 				     &start_addr_obj, &length_obj,
-				     &pattern))
+  if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "OOO", keywords,
+					&start_addr_obj, &length_obj,
+					&pattern))
      return NULL;
 
   if (!PyObject_CheckReadBuffer (pattern))